Modifying expansion forces by adding compression

ABSTRACT

A method for expanding a tubular in a borehole, the tubular having upper and lower ends, the system comprises a) applying a compressive load to the upper end of the tubular and b) expanding the tubular by moving an expansion device relative to the tubular while maintaining the compressive load. Step a) may include resting a weight on the upper end of the tubular or applying hydraulic pressure to the upper end of the tubular. The lower end of the tubular may engage the formation before step b) or as a result of step b).

RELATED APPLICATIONS

This application claims priority to application Serial No. 61/115,787and is related to application Serial No. 61/115,779, filed concurrentlyherewith, entitled “Modifying Expansion Forces by Adding Compression.”

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

TECHNICAL FIELD OF THE INVENTION

The present disclosure relates generally to a system and a method forexpanding an expandable casing in a drilled hole. More particularly, thepresent invention relates to methods for reducing the amount ofexpansion force that is required to expand the casing.

BACKGROUND OF THE INVENTION

Conventionally, when a wellbore is created, a number of casings areinstalled in the borehole to prevent collapse of the borehole wall andto prevent undesired outflow of drilling fluid into the formation orinflow of fluid from the formation into the borehole. The borehole isdrilled in intervals whereby a casing which is to be installed in alower borehole interval is lowered through a previously installed casingof an upper borehole interval. As a consequence of this procedure thecasing of the lower interval typically has a smaller diameter than thecasing of the upper interval. Thus, the casings are in a nestedarrangement with casing diameters decreasing in downward direction.Cements is typically provided between the outer surfaces of the casingsand the borehole wall to seal the casings from the borehole wall.

As a consequence of this nested arrangement, a relatively large boreholediameter is required at the upper part of the wellbore. Such a largeborehole diameter involves increased costs due to heavy casing handlingequipment, large drill bits and increased volumes of drilling fluid anddrill cuttings. In addition, the small diameter casing that is requiredat the bottom of the hole may not allow desired flow rates of drillingfluid. For these reasons, it may be desirable to expand the diameter ofone or more strings of casing so as to reduce the diameter reduction(s)that would otherwise be necessary. Expandable casings are known in theart.

Expanding the diameter of an upper casing interval allows lower casingintervals to have a greater diameter, since wider sections of pipe willfit through the expanded upper interval casing. Expansion of the casingmay be accomplished by passing a mandrel through the casing, among othertechniques. The mandrel is typically frustoconical in shape and has adiameter greater than the unexpanded diameter of the casing. In abottom-up technique, the mandrel is typically placed at the bottom ofthe casing interval before the casing interval is inserted into theborehole. In some instances, the expandable casing may be lowered intothe borehole on the mandrel. After the casing and the mandrel are placedinto the borehole, the mandrel is drawn upward through the unexpandedcasing, thereby expanding the casing.

If the expandable casing is resting on and supported by the mandrel,applying an upward force on the mandrel will cause the casing to moveupward. In other instances, the casing may not be supported on themandrel, but the available upward force on the mandrel is insufficientto overcome the expansion force required to begin radially expanding thecasing. In either case, it is desired to reduce the expansion force thatis required.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures form part of the present specification and areincluded to further demonstrate certain aspects of the present claimedsubject matter, and should not be used to limit or define the presentclaimed subject matter. Consequently, a more complete understanding ofthe present embodiments and further features and advantages thereof willbe acquired by referring to the following description taken inconjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic diagram depicting a system for expanding a pipe,according to one embodiment of the present invention;

FIG. 2 is a schematic diagram depicting another system for expanding apipe, according to a second embodiment of the invention;

FIG. 3 is a schematic diagram depicting yet another system for expandinga pipe, according to a third embodiment of the invention;

FIG. 4 is a schematic diagram depicting yet another system for expandinga pipe, according to a fourth embodiment of the present invention; and

FIG. 5 is a schematic diagram depicting yet another system for expandinga pipe, according to a fifth embodiment of the invention.

It is to be noted, however, that the appended drawings illustrate onlycertain embodiments of the present claimed subject matter and are,therefore, not to be considered limiting of the scope of the presentclaimed subject matter, as the present claimed subject matter will admitto other equally effective embodiments.

It will be understood that the Figures are not to scale and are notintended to illustrate the size or relative sizes of the components. Inaddition, it will be understood that the concepts that are illustratedherein with respect to a vertical borehole are equally applicable tocurved, deviated, and otherwise non-vertical boreholes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a first liner 124 is placed inside a borehole 126within a formation 128. If the well is offshore, borehole 126 is drilledfrom a rig resting on the seafloor, a floating rig, or other vessel. Inthat case, a riser 132, comprising a long tube of steel from the seafloor to a surface vessel, allows drilling mud to be pumped intoborehole 126 and returned to the surface.

As is known in the art, first liner 124 has an upper end 134, which maybe fixed in the borehole by filling the annulus between first liner 124and formation 128 with cement. Upper end 134 may be coupled to a blowoutpreventer (BOP) 138, which can be closed in the event that excessformation pressure threatens to blow out the well.

In a typical operation, a drilling cycle continues until the desireddepth is reached, whereupon the drill bit is removed and first liner 124is lowered into the borehole. First liner 124 is then expanded and/orcemented, if desired. The drill bit is then reinserted into borehole126, though first liner 124, and a second drilling cycle begins andcontinues until the next desired depth is reached. The drill bit isagain removed, and second liner 140 is inserted through first liner 124and into borehole 126. The outer diameter of second liner 140 is smallerthan the inner diameter of first liner 124, providing clearance assecond liner 140 is passed through first liner 124. Liner 140 has anupper end 144 and a lower end 146.

If desired, second liner 140 may be expanded, and the drilling cyclescan be continued through first liner 124 and second liner 140.Typically, one or more intervals of casing will already be positioned inborehole 126 before second liner 140 is placed in borehole 126.

Expansion of liner 140 may be carried out by pulling an expansion cone102 upwardly through liner 140. Alternatively, expansion may be carriedout by providing a hydraulic expansion device that provides a radialexpansion force and is moved incrementally through liner 140. Regardlessof how expansion is carried out, it is necessary to overcome the yieldstrength of the pipe in order to deform it to its expanded diameter.

Expansion cone or mandrel 102 preferably includes a narrow portion 104that can fit within liner 140 and a wide portion 106 that has a largerdiameter than liner 140. The wide portion 106 preferably has a diameterthat is smaller than the inner diameter of first liner 124, so that thatmandrel 102 can be removed from the casing and drawn up to the surfaceafter expanding liner 140.

Mandrel 102 is preferably suspended from a drill string 154 or otherguide string, such as are known in the art, that passes through liner124 and liner 140. As it passes through liner 140, mandrel 102 willplastically deform liner 140 radially outward, thereby increasing theinner diameter (and, generally, the outer diameter) of liner 140.

In accordance with one embodiment of the present invention, a pressuremechanism 114 is applied to liner 140 in order to facilitate expansionof liner 140. For example, in the embodiment of FIG. 1, a ballast pipe120 may be included at the upper end of second liner 140. Ballast pipe120 preferably remains within first liner 124 when second liner 140 hasbeen lowered to its desired depth. The weight of ballast pipe 120applies downward compressive force on the upper end of liner 140. Theweight of ballast pipe 120 and the weight of liner 140 itself result ina combined axial compressive load at the bottom of liner 140.

It has been found that applying an axial compressive load to anexpandable pipe decreases the radial expansion force that is required toplastically deform the pipe. Thus, applying a ballast pipe 120 to theupper end of liner 140 results in a reduction of the required expansionforce. When liner 140 is resting on mandrel 102, the added weight ofballast pipe 120 also results in an increased expansion force applied bythe expansion cone to the liner 140. Thus, if the required expansionforce is decreased and the applied expansion force is increased untilthe two become equal, the application of a ballast pipe or otherweighting device to the upper end of liner 140 can be used to initiateradial expansion of liner 140. Even if liner 140 is not resting onmandrel 102, such as in cases where liner 140 is resting on the boreholebottom, the added weight of ballast pipe 120 still results in areduction of the required expansion force. Thus, the use of a ballastpipe or other weighting device is advantageous regardless of whetherliner 140 is supported on the expansion device and regardless of whetherthe expansion device is moving upwardly or downwardly through liner 140.

During expansion, liner 140 will have an expanded portion 156 and anunexpanded portion 158. As mandrel 102 continues to be drawn upward fromlower end 146 toward upper end 144, expanded portion 156 will lengthenuntil there is nothing left of unexpanded portion 158. Mandrel 102 ispreferably sufficiently narrow to fit through first liner 124 and beretrieved from the surface when drawn upward by a pipe string or otherdevice 154.

It should be noted that mandrel 102 need not move upward relative tosecond liner 140; downward movement is also contemplated. Similarly, andas discussed below, liner 140 may be pushed downward over mandrel 102,or both items may move simultaneously relative to the borehole. Also,radial expansion force may be applied to liner 140 without use of amandrel, such as through application of hydraulic pressure or mechanicalforce. If desired, explosives or high-pressure chemical reactions mayalso or alternatively be used to move mandrel 102 through the pipe.

FIG. 2 is a schematic diagram depicting another system for expanding apipe, and includes at least one aspect of the present invention. Thevarious elements shown in FIG. 2 are similar to like-numbered elementsof FIG. 1. However, as shown in the system of FIG. 2, the ballast thatis shown as a separate device 120 in FIG. 1 may instead comprise part ofliner 140. For example, liner 140 will be slid entirely though firstliner 124 until a desired portion 142 is below liner 124. The portion143 of liner 140 that lies within liner 124 functions as a weightresting on the lower portion 142 of liner 140. As described above, theweight of upper portion 143 increases compressive force, reducesrequired expansion force, and may increase applied expansion force inlower portion 142. In this embodiment, it is preferred to provide means,such as are known in the art, for severing the portion of the pipe thatserves as ballast from the rest of the pipe, so that the ballast can beremoved from the borehole.

It will be understood that various other mechanisms for providing aweight or ballast pipe may be used. For instance, the ballast pipe mayhave a diameter that is unequal to the diameter of liner 140, with theresult that ballast pipe cannot rest directly on liner 140. In theseinstances, the weight of the ballast pipe can be transferred to liner140 by any suitable weight transfer mechanism at the interface betweenthe ballast pipe and liner 140. Devices for coupling the ballast pipe orweight to liner 140 include but are not limited to hooks, pegs, teeth,braces, or the like, which may engage corresponding holes, slots, ridgesor the like, or otherwise engage liner 140. The weight of ballast pipe120 is thus preferably supported until mandrel 102 has passed fullythrough expandable portion 142, whereupon the weight of ballast pipe 120is transferred to mandrel 102 for removal from the borehole.

Of course, if liner 140 is supported on the expansion device, it ispreferred that the total downward force at bottom of second liner 140not be so great that it overcomes the expansion force prematurely, orliner 140 would slide down over mandrel 102 before it was lowered to thedesired position. Thus, either the ballast can be applied to the upperend of liner 140 after liner 140 has been positioned at the desiredaxial position in the borehole, or the ballast can be applied when liner140 is not resting on the expansion device. In the former case, it willbe preferred to provide some means for preventing the expanded liner 140from falling downwardly into the borehole, such as by ensuring that theexpanded liner 140 engages the borehole wall. Alternatively, the bottomof the expandable can be supported by something other than mandrel 102,e.g. either the expandable is resting on the borehole bottom or thebottom of the expandable has been expanded (using a jack) and is “set”against the borehole wall. In that case, the added compression merelymakes it easier to expand the expandable.

Mandrel 102 may have a starting angle that provides a relatively largeaxial compression and a relatively small radial expansion to lower end146 of liner 140 as mandrel 102 enters liner 140. Mandrel 102 may alsohave an expansion angle that is more tapered than the starting angle andthat provides a relatively smaller axial compression and relativelygreater radial expansion than the starting angle as mandrel 102 movesthrough second liner 140. A reverse situation is also possible: mandrel102 may have a starting angle that is very tapered and that provides arelatively large radial expansion and only a relatively small axialcompression to liner 140. Mandrel 102 may also have an expansion anglethat is provides more axial compression and less radial expansion thanthe starting angle. Mandrels with more than two angles are alsocontemplated.

Ballast pipe 120 may comprise any suitable material and need not beexpandable. Any weight or other means of providing an axial compression,force or pressure on second liner 140 may be used as ballast pipe 120.Liner 140 is preferably fabricated of an expandable material. Thus,mandrel 102 simply carries ballast pipe 120 out of the borehole whenmandrel 102 is withdrawn from the well.

FIG. 3 is a schematic diagram depicting yet another system for expandinga pipe. The various elements shown in FIG. 3 are similar tolike-numbered elements of FIG. 1 and FIG. 2. However, as shown in thesystem of FIG. 3, ballast pipe 120 may be replaced by other means ofproviding axial compression on liner 140. If desired, for example, apressure mechanism 114 may include a cup 122 (or a gripper, or a wedge)adjacent to upper end 144 of liner 140. The application of fluidpressure behind (above) cup 122 will cause cup 122 to deform against theinside of liner 124, forming a seal. Further pressure will cause cup 122to bear on upper end 144 of liner 140. In this manner, cup 122 can applya compressive force to upper lip 144 of liner 140, thereby resulting inthe same benefits as ballast member 120. Stationary while an upwardcompressive force or pressure is applied to lower lip 146 of secondliner 140.

Referring now to FIG. 4 pressure mechanism 114 includes an alternativemechanism for providing axial compression to liner 140. In thisembodiment, pressure mechanism 114 includes a first diaphragm 148, whichmay be coupled to first liner 124, and a second diaphragm 150, which maybe coupled to upper lip 144 of second liner 140. First diaphragm 148 ispreferably not coupled to string 154. A hydraulic line 152 providesfluid access to the space 159 between first and second diaphragms 148,150. Pumping fluid through line 152 into space 159 results in theapplication of a compressive force to upper end 144 of liner 140. Incontrast to the embodiment shown in FIG. 3, the embodiment shown in FIG.4 does not require filling the entire volume of liner 124 withpressurized fluid. Hydraulic line 152 may comprise a hose or othersuitable device, such as are known in the art.

Referring now to FIG. 5, pressure mechanism 114 may alternativelyinclude a upper diaphragm 148 that is coupled to mandrel 102, ratherthan to first liner 124. Hydraulic line 152 supplies fluid pressure tothe space 159 between upper diaphragm 148 and lower diaphragm 150. Inthis embodiment, the fluid pressure will force lower diaphragm 150downward from first diaphragm 148, while simultaneously forcing upperdiaphragm 148 upward, thereby drawing mandrel 102 upward through liner140. Upper diaphragm 148 and lower diaphragm 150 cooperate to apply anaxial compressive force to second liner 140.

In the embodiments shown in to FIG. 4 and to FIG. 5, the application ofhydraulic pressure will result in increased compressive force on liner140.

In one implementation, the downward compressive force that is applied toliner 140 will approximately equal the upward axial force that isapplied by the mandrel. Accordingly, the upward axial force applied bythe mandrel and the compressive force in the second axial direction willprovide a net zero axial force, such that the only net force on the pipeis radially outward. In another implementation, the compressive forcethat is applied in the second axial direction will be substantiallygreater than the upward axial force that is applied by the mandrel. Inthis case, if the liner is not resting on something (such as theborehole bottom), the downward force may be sufficient to move the pipepast the mandrel. In another implementation, the bottom of the pipeengages the borehole wall such that the wall applies a downward force inopposition to the upward force applied by the mandrel. In this case, theapplied compressive facilitates expansion by reducing the requiredexpansion force. In another, less desirable implementation, the upwardaxial force that is applied by the mandrel causes the mandrel to moveupward through the pipe, while expanding the pipe.

In some embodiments, a jack may be used to initiate deformation (i.e.movement of the mandrel relative to the pipe). The pressure mechanismserves to increase compressive force on the pipe at the expansion point,thereby reducing the expansion (jacking) force.

Several implementations and embodiments have thus been described. Itwill be appreciated, however, that other implementations and embodimentswill also be substituted within the scope of this disclosure. Forexample, the mandrel may be replaced with an electromechanical device(such as a motor) that can apply a radial force that is greater than thetension within the drill string, and that is also greater than theweight of the fluid in the well. The electromechanical device may alsoinclude a sensor that can detect cracks or other structural problemswithin the pipe, and may be able to adjust a magnitude of the radialforce in accordance with an ability of the pipe to sustain the radialforce without damage.

Thus, although the invention has been described with reference toseveral exemplary embodiments, it is understood that the words that havebeen used are words of description and illustration, rather than wordsof limitation. Although the invention has been described with referenceto particular means, materials and embodiments, the invention is notintended to be limited to the particulars disclosed; rather, theinvention extends to all functionally equivalent structures, methods,and uses such as are within the scope of the appended claims.

1. A method for expanding a tubular in a borehole, the tubular havingupper and lower ends and an expansion device positioned below the upperend, the method comprising: a) applying a compressive load to the upperend of the tubular; and b) expanding the tubular by moving the expansiondevice toward the upper end of the tubular while maintaining saidcompressive load.
 2. The method of claim 1 wherein step a) includesresting a weight on the upper end of the tubular.
 3. The method of claim1 wherein step a) includes applying hydraulic pressure to the upper endof the tubular.
 4. The method of claim 3 wherein step a) includesforming a moveable fluid seal above the upper end of the tubular andapplying fluid pressure above the seal so as to cause the seal to bearon the upper end of the tubular.
 5. The method of claim 3 wherein stepa) includes forming a hydraulic chamber above the upper end of thetubular and applying fluid pressure within the chamber so as to causethe chamber to bear on the upper end of the tubular.
 6. The method ofclaim 5 wherein the expansion device is a mandrel and applying fluidpressure to the chamber also causes the mandrel to move relative to thetubular.
 7. The method of claim 1, further including the step ofengaging the formation with the lower end of the tubular before step b).8. The method of claim 7 wherein the lower end of the tubular does notengage the formation before step b).
 9. The method of claim 8 whereinthe lower end of the tubular engages the formation as result of step b).10. The method of claim 7, further including the step of resting thetubular on the bottom of the borehole before step b).